1. Field of the Invention
The present invention is in the field of valves. Particularly, the present invention is directed to a valve assembly which after actuation opens only for a predetermined time period and closes even if the initial actuating force remains in effect.
2. Brief Description of the Prior Art
Valves adapted for draining fluids from containers are well known in the prior art. There are many situations and devices where it is desired for a valve to stay open only while an actuating force is in effect. Construction of such valves often included a spring which causes the valve to close once the actuating force is released.
As a further development of the valve assemblies of the above-noted type (which do not stay open indeterminately after they have been opened) the prior art has developed valves which close within a predetermined time period (for example in 10 to 60 seconds) after the opening force is released. Such valve assemblies are sometimes used on water faucets to prevent waste, and are also used frequently in situations where fluid samples are periodically taken from containers. Thus, to actuate such "time limited" valve assemblies, one merely pushes a button, lever or handle (or the like), whereafter the valve stays open for the predetermined time period and then closes automatically. A problem of valve assemblies of this type is that the self-closing feature can be overridden, sometimes for mischievous or malicious reasons, for example by putting a weight on the valve handle, or by otherwise forcing the valve handle to stay in an "open" position. As a result, in many instances dangerously low fluid levels occur in the apparatus or containers to which the valve is mounted, and sometimes serious damage is sustained; even accidents and fires may occur as a result.
In light of the foregoing, there is a need in the prior art for a valve assembly which opens upon actuation for a predetermined time period, and which thereafter closes even if the actuating force remains continuously applied. In other words, there is a need in the prior art for a valve assembly in which the self-closing feature cannot be readily overriden by continuously applying force to the actuating mechanism of the valve. The present invention provides such a valve assembly.